1. Field of the Invention
The present invention relates to an adhesive force development unit, an adhesive-label issue device, and a printer each for developing an adhesive force in an adhesive label.
2. Description of the Related Art
Conventionally, as label paper for an adhesive label to be used as a POS label for food, a distribution/transportation label, a medical label, a baggage tag, an indicator label for a bottle/can, and the like, there has been widely known label paper constituted by a recording surface (a printed surface) formed on a front surface of a base material, an adhesive layer formed on a back surface of the base material, and release paper (a separator) coating the adhesive layer.
In a case where this type of adhesive label is used by being attached to an adherend, it is necessary to peel off the release paper on the back surface from the adhesive layer after predetermined information such as a bar code or price is printed on the recording surface. However, it is practically difficult to collect and recycle the release paper which has been peeled off, which causes a problem that the release paper becomes industrial waste.
In view of this, from the viewpoint of environmental conservation and reduction of environmental impact, adhesive labels which do not use release paper have been used recently.
The adhesive labels which do not use release paper are, for example, as follows. Initially, there has been known an adhesive label (a first adhesive label) in which a mold releasing agent such as a silicone resin is applied on a surface of a recording surface, so that releasability between the recording surface and an adhesive layer is secured even if the adhesive label is wound into a roll. Further, there has been known an adhesive label (a second adhesive label) using a heat-activated adhesive layer which develops adhesiveness by heating an adhesive layer.
Further, another adhesive label (a third adhesive label) different from the first and second adhesive labels is also devised. FIG. 11 is a view illustrating a multilayer structure of an adhesive label 200. As illustrated in FIG. 11, the adhesive label 200 includes a multilayer structure in which a base material 201, an adhesive layer 202, and a resin film 203 are laminated. The resin film 203 is formed by using a polyester film and has a thickness of 1 to 3 μm. At the time of use, holes are formed in the resin film 203 by means of needles 210, or a stretching polyester film is used as the resin film 203 and holes are formed in the resin film 203 by a heating technique, e.g., thermal head heating, thereby breaking the resin film 203 to expose a lower adhesive layer 202 so that an adhesive force is developed.
In the meantime, in the adhesive label, a viscosity (fluidity) of an adhesive compound in the adhesive layer 202 and a thickness of the resin film 203 have a strong correlation with each other. That is, in order to develop an adhesive force in the adhesive label 200, after holes are formed in the resin film 203, it is necessary to cause the adhesive layer 202 to rise to a front surface of the adhesive label 200 at a side of the resin film 203 through the holes.
Therefore, as a thickness of the resin film 203 is larger, a pressure to attach the adhesive label 200 should be made stronger, which causes a problem that its convenience is impaired.
On the other hand, it is conceivable that a viscosity of the adhesive layer 202 is reduced so that the adhesive layer 202 easily rises to the front surface at the side of the resin film 203.
However, the adhesive label 200 is generally supplied as continuous-form paper (rolled paper) wound into a roll as illustrated in FIG. 12, the wound adhesive label 200 receives a certain pressure in its thickness direction under the influence of a tension caused by winding the adhesive label 200. In this case, as illustrated in FIG. 12, if the viscosity of the adhesive layer 202 is too low, an adhesive compound 220 might be pushed out to leak from end faces located at both sides of the adhesive label 200 in its width direction. This may cause a so-called blocking phenomenon, in which adhesive labels 200 stick to each other because of the adhesive compound 220 thus pushed out.